For piezoelectric ceramics used for piezoelectric elements, e.g., piezoelectric actuators, ultrasonic transducers, piezoelectric sounders, and the like, lead zirconate titanate (PZT) based piezoelectric ceramic capable of obtaining a large piezoelectric constant has been used widely. Furthermore, in order to improve the characteristics of the PZT based piezoelectric ceramic, many types of three-component piezoelectric ceramics containing the third component have been developed.
The piezoelectric ceramic represented by PbTiO3—PbZrO3—Pb(M21/3Nb2/3)O3 (where M2 represents a divalent metal element, e.g., Ni or Zn) has been noted as the three-component piezoelectric ceramic.
For example, Patent Document 1 describes a ferroelectric ceramic having a basic composition composed of 43.5 percent by mole of PbTiO3, 44.0 percent by mole of PbZrO3, and 12.5 percent by mole of Pb(Zn1/3Nb2/3)O3 and containing small amounts of Bi and Zn to realize a ferroelectric ceramic capable of obtaining a good temperature coefficient of dielectric constant and having improved sinterability.
Furthermore, Patent Document 2 describes a piezoelectric ceramic composition containing a composition represented by (PbuA1-u)v{(Zn1/3Nb2/3)xTiyZrz}2-vO3, 0.7 to 3 percent by mole of Mn in terms of MnO2 relative to the above-described composition, 0.7 to 2.4 percent by mole of Al in terms of Al2O3 relative to the above-described composition, and 0.1 to 1.5 percent by mole of Si in terms of SiO2 relative to the above-described composition, where in the above-described composition formula, A represents at least one element selected from the group consisting of La, Nd, Pr, and Bi, u and v satisfy 0.92≦u≦0.99 and 0.97≦v≦1.03, respectively, and x, y, and z satisfy 0.06≦x≦0.18, 0.43≦y≦0.53, 0.29≦z≦0.51, respectively, and the relationship represented by x+y+z=1 is satisfied, as a piezoelectric ceramic component which can be fired at a temperature of lower than 1,150° C., which has a large qm, and which exhibits a small reduction in qm due to high electric field driving.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 3-40965
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-181037